These speedy serpents can move faster than most people can run, a fact that partly explains why they are so feared. Viernum said, “Black mambas are one of the fastest species of snakes, reaching slithering speed up to 12 mph [19 kph].” This is undoubtedly fast, but still slower than the myths of them outrunning horses would suggest. Over longer distances, they average about 7 mph (11 kph).